A British anti-war campaigner is travelling to Iraq to appeal directly for the release of hostage Norman Kember, who was kidnapped on Saturday.
Mr Kember protested against the war in Iraq
Iraq war opponent Mr Kember, 74, of Pinner, London, was seized in Baghdad with two Canadians and an American.
The anti-war movement, representing the Muslim Association of Britain, Stop the War and CND, said leading activist Anas Altikriti would fly to Iraq.
But it admitted the mission was "far from safe or guaranteed".
Mr Altikriti, who is of Iraqi origin, told the BBC News website he had agreed the trip with the group of Christian peace activists with which Mr Kember had been working in Iraq.
"I will liaise with Christian Peacemaker Teams (CPT) when I arrive and we will agree an action plan together," he said, before flying out to Iraq on Thursday.
He said he was going in a personal capacity, but that he had told the UK Foreign Office about the mission.
"Our main concern, and theirs, was that we did not want to jeopardise any moves that people were already making to secure Mr Kember's release," said Mr Altikriti.
He said he would make contact with people in Iraqi society, non-governmental organisations and political parties that may have "some kind of leverage" with the kidnappers.
He would also be working with local media to get the message across that Mr Kember is a "friend of the Iraqis," he said.
A statement from the British anti-war movement said Mr Kember was a well known member of the anti-war effort and took part in the dozen or so demonstrations held in protest against the war and occupation of Iraq.
Mr Altikriti said he realised Iraq was still a risky place to go
"The movement acknowledges that this is far from a safe or guaranteed mission, but we hope that Mr Altikriti's mission will have a successful conclusion," it added.
The groups said they had been following events since the abduction with growing concern.
"What was hoped to be an incident ending in a quick release of the hostages is gradually developing into one that could be with dire consequences."
The Muslim Council of Britain urged Mr Kember's captors to release the Briton and his fellow hostages unharmed.
Secretary General Sir Iqbal Sacranie said: "Norman Kember is a man who cares deeply for the people of Iraq, and his kidnap and continued detention is completely unjustifiable.
"Our faith of Islam holds in great esteem the peaceful bridge-building work that Mr Kember was involved in."
On Wednesday Mr Kember's family said he is a man who has "spent his life promoting peace".
Earlier this week he was shown in a video filmed by his captors in Iraq.
Mr Kember, American Tom Fox, 54, and Canadians James Loney, 41, and Harmeet Singh Sooden, 32 were pictured sitting on the floor.
The previously unknown militant group, the Swords of Truth Brigade, claim their captives had been undercover spies working as Christian peace activists.
Before travelling to Iraq, Mr Kember had said the trip was designed as a "gesture of solidarity" with peacemakers working in the country.